A coin-cell battery is required for power loss indication.
A beep will sound when the device loses power.
It uploads all data to the server for reporting and must be permanently powered. If unplugged, it will beep until it is plugged in again. The DCS must be mounted at a high location for best signal strength.
Unplug the unit at the wall socket and wait 30 seconds. When the unit starts beeping, plug it back in and the reset procedure will complete.